This invention relates to semiconductor memory arrays, and in particular to charge pumps for providing programming voltages to conductive lines such as word lines and bit lines in programmable semiconductor memory arrays such as electrically erasable read-only memories (EEPROM).
Programming floating-gate non-volatile semiconductor memories such as EEPROMs typically involves charging up memory word lines (x-lines) and bit lines selected for programming. Specialized on-chip charge pumps can be used for selectively charging selected word lines and bit lines. As the space between the high-voltage nodes and the carrier injection points of the charge pump circuit decreases, the problem of carrier injection into the circuit substrate increases in importance. Carrier injection or escape occurs when conductive channels in active devices are driven to switch potential from high to low or low to high. Carrier injection into the circuit substrate and subsequent migration of electrons to the high-voltage nodes of the circuit can significantly degrade the pumping efficiency of the charge pumps.